This invention relates generally to television receiver tuners and specifically to television receiver tuners for use in digital high definition television receivers.
High definition television receivers will very likely incorporate double conversion tuners in which the input RF signal is upconverted to a very high frequency (on the order of 1 GHz or more), filtered and downconverted to a standard 44 MHz IF frequency. Ideally, the frequency response characteristic of the tuner is substantially flat over the tuned frequency band. While the ideal is seldom attainable, various adjustments to the gain characteristics of the RF section of the tuner can help to provide the best compromise between protection from undesired signals and noise. Presently available wideband AGC circuits do not have the desired range of attenuation and precision for such tuners and the present invention is directed to making a precisely controllable AGC circuit for a high definition television tuner.